Mobile Data only working when used as hotspot

I recently bought a HTC One. Everything worked fine including mobile-data and Wifi. Until I once used my phone as Hotspot for my laptop.

The whole time while using the hotspot I had working internet on both my phone and laptop. But the next day (hotpost disabled), I couldn't get the mobile-data to work.

I don't get an error, it just doesn't load.

Wifi connections still work.

Now I tried reenabling hotspot and to my surprise it works. I now have internet on the laptop but NOT on the phone.

It seems that somehow the mobile-data will only work when the phone is used as hotspot.

What have I done wrong?

Android 4.2.2

Answer

Somehow there was a proxy set up in the APN settings …

Edit: To change the proxy you have to go to the settings and click on mobile data. Select Access point names, select the active APN (or the one you're having problems with) check/reset the Proxy/Port settings.